The stress of waiting for A-level grades - due to be published this Thursday - could be damaging teenagers' health, a snapshot study suggests.

Hertfordshire University researchers found 21% suffered from depression, 12% from insomnia and that 8% had experienced panic attacks.

One in 10 of the 123 sixth-formers interviewed had sought medical help.

The university said 35% of students did not have a back-up plan if they achieved poor grades, adding to stress.

'Nerve-racking experience'

Alastair McFadyen, head of admissions at Hertfordshire, said: "Results time is an incredibly nerve-racking experience and more than four in 10 school leavers have considered leaving education as a result of not knowing what to do or how to get a university place.

"But there are many avenues available. Options such as the clearing process often give students a better opportunity at finding the right course and university whether their results are better or worse than expected."

Clearing, which involves students applying after A-levels, is run by all UK universities.

More than 38,000 people find places using this service every year.

Around 250,000 A-level candidates will find out their results on Thursday. Grades are expected to improve for the 22nd year in a row.